Sandals are an open type of footwear, consisting of a sole held to the wearer's foot by straps passing over the instep. People usually wear sandals in warmer climates or during warmer parts of the year in order to keep their feet cool and dry. A sandal has a sole or foot support made from rubber, leather, wood, tatami or rope. It may be held to the foot by a narrow thong that generally passes between the first and second toe, or by a strap or lace, that passes over the arch of the foot or around the ankle.
Sandals may have different varieties. For example, flip-flops are a type of open-toed footwear sandal, typically consisting of a flat thin sole held loosely on the foot by a Y-shaped commonly strap that passes between the first and second toes and around both sides of the foot. They may also be held to the foot with a single strap over the top of the foot rather than a thong. Although flip-flops may provide wearers with some mild protection from hazards on the ground, due to their simple design and lack of support, flip flops generally are not considered the best footwear, especially for individuals with flat feet.
Innovations have been made to push the boundary for wearing comfort of sandals. U.S. Pat. No. 6,523,206 discloses a custom formed orthotic sandal to a biomechanically corrected shape of a user. A negative cast is taken of the user's foot to obtain the proper shape for the sandal. A positive impression cast is then formed from the negative cast to correct for biomechanical abnormalities of the user's foot. The custom orthotic sandal is formed by adhering a moldable material on the sole of the sandal. U.S. Patent application 2005/0050768 discloses a sandal for accommodating the normal mechanics of the foot. The sandals have a predetermined shape and degree of inclination for the rear foot bed, which incorporates layers of different materials. U.S. Pat. No. 7,854,075 discloses an orthotic insole reusable in open shoes. The insole has an adhesive layer which securely but temporarily bonds the insole to a shoe. The supporting insoles include an arch support and a heel lift.
However, the above innovations may either have production cost issues for mass production or delamination issues due to the multiple layer structure. It would be desirable to provide sandals with biomechanical foot support, robust usability and cost-effectiveness.